His reign was remarkable for the influx of Portuguese traders, mercenaries, and early Modern warfare technology.
The Pali text "Sangitiyavansa", authored in the reign of King Rama I by the Venerable Vanarata of Pho Temple, state that he is the nephew (son of the sister) of Ramathibodi.
[3]: 72 In 1539, King Tabinshwehti attacked the Mon people inhabiting Chiang Kran, which was under Siamese rule.
Chairachathirat "marched against Chiang Kran" with the aid of 120 Portuguese traders in Ayutthaya[2]: 37 and drove the Burmese back.
Chai's half brother, Prince Thianracha, became regent but entered a monastery to escape the ensuing power struggle.